This invention relates to an exhaust gas turbocharger for an internal-combustion engine of the type having a radial turbine with exhaust gas supplied in the radial direction to drive the turbine blades.
On the basis of German Pat. No. (DE-PS) 31 35 107, an exhaust gas turbocharger of this type is known, the turbine of which has a bypass. The bypass comprises a shutoff device that can be actuated by means of an actuating drive and influenced by the detected operating parameters of the internal-combustion engine. However, in this case, it is a disadvantage that the efficiency of the exhaust gas turbocharger in the lower speed range is still unsatisfactory. In the case of today's small radial turbine housings, a flow occurs against the blades of the turbine wheel that is high in losses, especially in the lower speed range. This flow results in an extreme thrust flow and negatively influences the consumption behavior of the internal-combustion engine because of the flat flow against the blades.
It is an objective of the invention to improve the efficiency of a radial turbine in the lower speed range.
According to the invention, this objective is achieved by providing an exhaust gas duct opening in the axial direction of the turbine wheel at the turbine housing on the side of the turbine wheel shaft.
Further features of preferred embodiments of the invention involve the structural arrangement of separate exhaust gas ducts formed in the turbine housing and control devices for controlling the relative exhaust flow between the exhaust gas ducts as a function of the turbine speed and/or changing air output pressure.
The radial turbine arrangement constructed according to the invention has the further advantage that the blades of the turbine wheel of the radial turbine of the exhaust gas turbocharger are designed for two different operational ranges. Thus the blades have a physical bend which, in the case of a radial flow feeding in the upper speed range of the exhaust gas turbocharger, permits a flow against the blades that has few thrust losses. In a lower speed range of the exhaust gas turbocharger, the feeding of the flow takes place approximately semiaxially to the blades with improved operation at these speeds. On the basis of the blade bend along the axial extension, a flow against the blades is also obtained in this lower speed range that has few thrust losses so that the nonsteady behavior in the lower speed range of the exhaust gas turbocharger is significantly improved.